text:
What type of aircraft is this Airplane in Riga (junkyard)?
My relationship with the Mil Mi-6 led me to this Wikimedia photo of a time-worn Mi-6 in Riga airport.
In the photo there are the Mi-6, a Skoda Fabia, some picnic equipment, other stuff and a supersonic jet fighter (is it really a jet fighter?) with a large, red "43" on the nose. Here it is a detail from the wikimedia photo

What airplane is the "43" red?

Bonus points for the white "27" on the left (but it's difficult because you have just a detail of the nose) and the jet bomber (?) on the right, partly hidden by the red metal ladder.

The white-nosed glider below the Su-7BKL ("27") is a L-13 Blanik.

I have been misguided into asking from the junkyard appearance in the photo. If I had imagined that it is instead the Riga Museum of Aviation, with a well organized site...

@gboffi it is somewhat junkyard-like, and in my initial search I found some Tripadvisor reviews calling it exactly that. It may have improved a bit in the years since, however.

it's amazing what a telephoto lens can do to a scene.

An Su-7U. I initially confused it with a Mig-21 and later with an Su-17 due to the similar nose cone, but you can see the exact airframe on the Museum's website:

The wing fences are a giveaway, as is the tail shape and slightly less prominent intake cone.
From the museum website:

At the beginning of 1960's Sukhoi Design Bureau finished to develop its new fighter-bomber Su-7B («Fitter») and another important task arised — to make two-seat training variant of this type. This objective was urgent because Su-7B was hard to control, especially on landing and critical flight stages. Two-seater, designated Su-7U («Moujik»), destined to make training process easier and quicker for pilots.
Nevertheless Sukhoi team managed to release first Su-7U prototype only in October, 1965 due to its high workload connected with evaluation of Su-7B and another projects. Trainer was a bit longer than Su-7B, also was unmounted one of the two cannons in order to reduce weight. The rest of the armament remained mostly the same. Crew seats were located behind each other under the separate canopies. Rear canopy was equipped with large retractable mirror to improve instructor's field of view on take-off or landing. Also instructor had full set of instruments and controls and was able to interfere in flight whenever he decided. Emergency ejection system allowed crew to leave aircraft in dangerous situations separately and safely.
Su-7U production commenced at Komsomolsk-na-Amure Aviation Factory in 1966 and continued till 1971, together with Su-7BKL and Su-7BMK manufacturing. Two-seater' export modification Su-7UMK was bought by Algeria, Afghanistan, Egypt, India, Iraq, Syria, North Korea, Poland, Czechoslovakia and took part in 1970-80's wars and conflicts. Soviet Air Force used Su-7U for very long time — till beginning of 1990's, because of its similar performance with Su-7B's successor Su-17.
Museum's Su-7U serialled 43-red and has production number 2318.

"27" is a Su-7BKL "Fitter". The museum says:

In Su-7BKL was invented new wheels-and-ski landing gear, gunpowder
  accelerators, two-canopy breaking parachute, increased amount (six) of
  weapons pylons, upgraded bombsight. New gears were adopted for
  taxiing, take-off and landing on soft-surface aerodromes. Front gear
  received tyre with increased diameter and on main landing gear were
  installed small steel skis, together with wheels. During take-off or
  landing on hard surface were not working due to their suspension, not
  allowing to touch the runway. But they started to work when wheel
  became to deepen into soft soil. Skis helped to distribute pressure
  and not allowed wheels to get deeper and to brake aircraft movement.

Apparently it's been in Riga since the mid 1980s.

source

It's a Su-7 as well as the "43" red,  but in my photo "23" stays at least 50 cm lower, is it the different landing gear?

If you look closely you'll see that the nosewheel of "43" is not on the ground, hence the discrepancy - it's sitting tail-heavy with its nose pointed upwards.

I looked closely, the nosewheel is not on the ground indeed... good catch.

The aircraft behind is, I think, the more interesting of the aircraft, a Tu-22M1 Backfire, with its prominent refuelling probe.
It is the pride of the collection of the Riga air museum:

The bomber transferred to the museum in the early 90's. In the museum
  bomber drove in three tractors! And in the mid 90s, the Americans saw
  from the satellite to the territory of the Riga airport Tu-22M1, came
  and gutted the electronics and the nose of the bomber. Currently, the
  Tu-22M1 is in our museum and is the pride of the collection.

 source

The yellow box text is gibberish, probably a machine translation. Does it imply that the Americans saw it from satellite, and then came and took the electronics out of its nose? Sounds unlikely, and now I am curious.

@MikeWise: I agree that the translation is awful, but the story sounds at least vaguely plausible. Based on the timeline, I assume the bomber ended up in Riga in the aftermath of the breakup of the Soviet Union. And I can believe some US intel clerk examining satellite imagery a few years later, spotting what looks like an ex-Soviet bomber sitting in now-friendly territory and suggesting that it be investigated. (Remember this was way before Google Maps, and indeed before Google; the Internet was still in its infancy, and the museum likely had no web page yet.) Details would be nice, though…

@MikeWise the russian version of the description at http://ru.airmuseum.lv/blog/tu-22m1/ says the exact same thing, so while it's interesting if it's an accurate description of what happened, that's what the museum people are asserting.

To me it looks like a Sukhoi jet bomber SU17, SU20 or SU22
https://en.wikipedia.org/wiki/Sukhoi_Su-17

Su-20 RB3 taken from Wikimedia

@AEheresupportsMonica Could you please post in a comment your link to the Riga "Aviation Museum" that I had not the time to copy...

I've rewritten my answer and found a better link from the museum itself. Note it's not an Su-17, but its predecessor.

It seems that "43" red is indeed a SU-xx, but the characteristic air intake just ahead of the cockpit is hidden by ... a beach umbrella!

Yeah, that threw me off, but it is not a Su-17 either! At least according to the museum itself.

@AEheresupportsMonica the "predecessor" of SU-17 is the SU-15 which has no air intake at the nose: https://upload.wikimedia.org/wikipedia/commons/thumb/c/c3/Su-15_Flagon.jpg/450px-Su-15_Flagon.jpg

@TimothyTruckle predecessor in the sense that Sukhoi designed the 17 based on the 7.

@AEheresupportsMonica but the SU-7 does not have the "tunnel" behind the canopie, so it is not the one on the picture. https://upload.wikimedia.org/wikipedia/commons/1/1e/Sukhoi_Su-7BKL%2C_Poland_-_Air_Force_AN2202869.jpg

@TimothyTruckle because the one in Riga is the U trainer version, see here: https://upload.wikimedia.org/wikipedia/commons/c/ca/Su-7UMK-1998.jpg Also the 17 does not have strakes along the spine.


text:
What should I look for if I am safely in the air with no means of braking at all
So I just saw this answer, and there was a ravine at the end of the runway. I have decided to open the throttle again and go for the ravine. I dropped about a 100 ft in to the ravine, but managed to gain altitude again. I have enough fuel for a few hundred miles and all kinds of terrain are near enough.
What should I look for to maximize our chances of survival?
EDIT: With no means of braking, I mean no brakes, no spoilers or thrust reverses. So no way of slowing down except for drag from air or the ground.

What type of aircraft? Are you interested in terrain types only, or also obvious tips like to avoid cities and find the longest stretch of flat space available?

It's purely hypothetical, I had a medium size commercial aircraft in mind. I'm not only thinking about terrain, but completely obvious suggestions are not very useful. My first thought was a dessert, but soft sand could cause the aircraft to flip over if the nose digs in, so on second thought that seems a very bad idea.

In its current form your question is a duplicate. It’s already answered: an airport with EMAS. Also some airports, especially military might have nets that could be used depending on the size of your plane.

@Antzi: That is possibly the worst solution one can find. An EMAS is used if it is not possible to fulfill the requirements for free space behind a runway, so there is always a dangerous obstacle behind it. An EMAS is also not designed for high speeds, usually around 70 Knots or so. So a runway without EMAS would generally be much better.

If your aircraft is heavy enough to start to crush the EMAS, that's a really effective (and safe) solution. Not so much if it's too light.  That said, the question is extremely vague & lacking in necessary details - VTC.

@RalphJ: EMAS is not suitable for high speeds. Can you tell me what details you are missing?

You always have some sort of braking available.
If its not traditional wheel brakes, you can pull full up-elevator and open doors to introduce a lot of aero-drag.  You can slalom the wheels, snaking down the runway.  You risk a ground-loop or flip, but that is very survivable.  If you have retractable gear, you can belly land, and will slow down quickly as you slide.  Since its a purely "hypothetical" question, you have many options for slowing down.

Missing details: aircraft type (C-172 or B-777), actual location (west coast near Edwards or Salt Lake, or Eastern US with no large dry lakes but many 12,000' runways available), actual range (failures enough to disable all braking may disable gear retraction = reduced range), significant weather conditions (strong headwind vs calm + wet runway) for starters.

At the risk of stating the obvious, an airport with a large runway would seem to be the first thing to look for.

@RalphJ: It is obvious that those details are completely irrelevant, or were you planning planning on investigating the area I name for an hour to find suitable locations and then calculate if the specified aircraft can reach it?

As per your own suggestion, I'd go for desert, or any other plain terrain if no suitable large airports are availlable. As your question is about a medium size commercial aircraft, there is pretty much no chance of flipping the plane over its nose. If the soil is soft, the landingear will sink into it and either slow the plane down or shear off.
Landing technique would be to make a smooth landing, and if the ground appeared to carry the weight, keeping the nose up for a mildly prolonged time would provide aerodynamic braking.
The danger in off site landings is losing directional stability, skidding sideways,snapping a wing and doing a flame enhanced series of rolls.

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Why do flight control cables not slacken during the cold temperatures at cruise?
Image source
Flight controls in airliners have long cable lengths in between the cockpit controls and the control surfaces. For instance in the picture above: the pilot operates the yoke, which deflects a steel cable running through the front fuselage and the wings, which then opens a servo valve for the hydraulic actuator moving the aileron.

The cables are made of steel, the aircraft from aluminium.
Thermal expansion of aluminium is twice that of steel.
The aircraft can be standing in the sunshine at 40°C, and half an hour later be at cruise altitude at -50°C.
The difference in thermal contraction would cause a couple of centimetres slack in the cables at cruise, with the pilot then experiencing a control deadband: turn the yoke some degrees and nothing happens. Or the cables would be appropriately tightened for the cruise situation, causing tight cables and high control friction at take-off: try to turn the yoke by pushing hard.

But the forces and (lack of) deadband are identical at take-off and cruise. How is this possible?

Edit
Yes there is a Cable Slack Takeup drawn in the picture, but the working of it is a little bit more complicated than it seems, I've added an answer below.

Wouldn't tension increase at colder temperatures?

@acpilot aluminium shrinks more than steel does...

I wonder how many early aircraft crashed and burned before engineers figured this out and came up with the cable slack take-up spring solution. Great question.

I would say your answer is in the image you posted. "cable slack take up"

Do you have any data justifying that the slack is at all significant? My garage door opener works perfectly both at +35C and  at -40C.

@MartinArgerami Have put it in an answer, see below.

@DJ319 Some people ask questions when they actually know the answer.

I didn't realise,

If you look closely at your drawing you will see the cables are not really simple pull cables but really act like steel belts. That is, there is a pulley at each end and when you actuate the control the cable is rotated around the system in a loop.
The end pulleys and or idler pulleys are spring loaded to maintain a predefined tension on the cables and should take up any slack in the system caused by operation, temperature, or aging of the cable.

If the top left pulley above is the yoke in the cockpit, and you turn it, the top cable rotates around the loop, like a belt, and turns the actuator bottom right. Note that also means when you turn the yoke, it does not pull significantly on the springs, the cable just rotates.
Interestingly, the Concorde had to handle both contraction and expansion. When cruising at supersonic speeds the aircraft stretched up to about ten inches.
ADDITION:
For non looped cables, and occasionally for looped cables where the cable needs to traverse between objects that move relative to one another, cable housings are also used.

You are probably familiar with these on bicycles. The trick to them is the ends of the housing are attached, or anchored, to the frame somewhere. The housing is flexible so can be arranged in a loop or s-shape that can be extended or compressed as the fixed end points move relative to one another.
The control cable on the other hand always has a fixed length within the housing despite the change in the end positions.
The issue with these though is friction is high compared to pulleys, the inside of the housing can become contaminated with dirt and debris, and it is impossible to inspect the cable within the housing.
As with the looped system, a spring is still required, usually at the business end, to pull back on the cable. In the single cable case, actuating the cable from the control end also involves pulling on the spring.

..the cables are not really cables but really steel belts. Not sure what you mean by that?

@Koyovis it acts like a belt, they are cables, but they are looped like a belt.Looking at the image in my answer, if the top left is the yoke in the cockpit, and you turn it, the top cable pulls and rotates the pulley bottom right, the bottom half of the loop, obviously, goes the other way at the same time.

@Koyovis that means when you turn the yoke, it does not pull on the spring, the cable just rotates around the loop.

yes it does work in a loop that way. However, the solution you've drawn has a problem in that you can wind up the pulley against the springs: if the aft pulley is in a servo valve stop, you can still deflect the yoke by stretching both tensioning springs. The cable stiffness is now in series with the tensioning springs, which cannot be too stiff because of high friction and side load on the middle wheels in your drawing. So the tensioning springs do their job, but the whole control system either feels sloppy or has a high friction load/side load.

The Concorde is not the only aircraft handling contraction/expansion... The SR-71 Blackbird was actually leaking fuel while on the ground, since the tanks only sealed at high temperatures resulting from the extremely high speeds.

@Koyovis no, it does not work that way. The only time it can pull the pulley is if the pulley itself sticks, or rather, fails to rotate. However, having said that, the diagram is only intended to show how the cable works as a belt. The actual actuator may not be the last thing in the loop, and the tensioners can be anywhere along the lin. Yes, the tension on the cables IS very high, by design, and side-load at the turns is indeed a design factor.

@Koyovis Since cable systems must be either sloppy or have high load they are always designed with high load to avoid being sloppy. Now, how do you reduce friction at high loads? Bearings.

What a great answer!

Cable tension is applied with turnbuckles and/or with a cable tension regulator. Cable loops are not put in series with springs.

@Koyovis whhow do  you think a cable tension regulator works.... you are right, static Cable tension is adjusted with turnbuckles though.

Check below for how a cable tension regulator works.

@Koyovis it's still controlled with a spring. It does not matter how many fancy levers etc you add, it's still a spring.

They probably do, but there are springs that take up the slack. In fact the diagram you posted shows it. Its called the "cable slack take-up."
See the little spring in the bottom center.

So then we're not only stretching the cable but also deflecting slack-spring?

The tension is on the pulley, so the wheel of the pulley continues to turn just the same even if there is slightly different tension on the pulley by the spring, thus preserving the deadband at different temperatures/cable lengths.

Cables can only transfer tension loaded forces, that is why we need two cables in order to be able to deflect into two directions: the control cables going from the cockpit to the control surfaces can be seen as a loop, as Trevor correctly identifies.

Sloppiness

Cables also stretch, and for applying remote loads that is a disadvantage. The cable stretch is in series to all the dynamic and static behaviour of the flight controls: mounting a sloppy cable results in vague and inconsistent stick behaviour, and a feel as if the pilot is stirring in a pot of soup. The feel spring stiffness is diluted by the cable stiffness, and can never be higher. Cables must have high stiffness, so let's tension them up, let's give them a high pre-load.
However, putting a high pre-tension on the cables causes high structural forces. The cables run over pulleys, which are mounted on a bearing fastened to a structural member. One bearing. So the pulley loads the bearing with a torsional load and the cable tries to skew it, not a good situation for a cable run. It might run off the pulley and get stuck, resulting in an aircraft that cannot be controlled and a crash. Unfortunately everything in an aircraft must be light and bendy and we cannot beef up the bearing housing.

Two-sidedness
So we cannot put a very high pre-load on the cable. But a certain amount of pre-tension is beneficial:

Cables only pull, and the cable not pulling may not be slack, otherwise it could run off as well.
Pre-tensioned cables can provide push loads, by reducing the pre-tension it was subjected to.

Variability
An aircraft is a structure subjected to a variability of loads:

Wing tips bend upwards during flight, bend upwards more when fuel runs out, and slam down at landing.
As mentioned in the OP, the structure expands and contracts as a function of temperature. Thermal expansion is 23.1 µm/(m·K). A 747 is 70 m long, temperature differences of 90 °C can be reached, so the resulting stretch is 15 cm. Steel cables stretch half that amount, and the total cable run is differs 7 cm from the temperature alone.
During flight, the elevators & tail plane put up/down loads on the fuselage as well, bending it up/downwards. Ailerons bend the wings more or less.
During turbulence, the wings flap up and down.
After spending 12 hours at -60 °C at cruise altitude, the fuel in the wing is very cold and only the lower wing skin is exposed to it. The upper wing skin is exposed to the sun, and upon approach gets warmed up more and more: upper skin stretches because of the heat, and the wing tip comes down by a surprising distance.

So all in all, the flight control cables must accommodate a difference in length that in a large aircraft is in order of magnitude of 10-20 cm. The control cable has a diameter of 3-5 mm. Steel elastic modulus is 200 GPa, a stretch of -0.2/70 m/m causes a tension of 500 MPa, twice that of structural steel, and a force of 4,000N (800 lb). Way too much. Yes you can increase the cable thickness with associated heaviness, but best to reduce the pre-load to the level where the non-pulling cable still has some tension.

The solution
We want some pre-tension in the cable loop, but not too much. We want it to not vary with varying length and bending, it must be always constant. And we want high differential stiffness: nice and easy springiness when not deflected, very high stiffness when deflected. What to do?
Image source
The solution is indeed in applying a spring, but not one that is attached to the aircraft structure:

The "wheel" is not a multi-rotation unit, but two cable quadrants that deflect about 40 degrees each total.
Springs pull them towards each other when no load is applied, when the pilot does not apply a force to the stick.
A blocking mechanism prevents the two halves from moving relative to each other when the pilot does apply a force. A more detailed description is found in the image source above.

So while the flight controls are trimmed, the cable is tensioned nicely and accommodates varying circumstances. When forces are applied, this mechanism is partially blocked, only lightly when light forces are applied.

'Cables must have high stiffness, so let's tension them up, let's give them a high pre-load." Preload makes sure that the stiffness of the cable is present regardless of input force (as long as the pre-load is higher than the input force), it does not add additional stiffness. Also, could you give sources for your information and diagram? I'm really curious how and why this blocking mechanism is present.

@Sanchises Total effective stiffness is higher when preloaded because the non-pulling cable contributes to the force transfer, effectively doubling the cross sectional area. The source of information is a uni lecture from long ago, sadly I don't have the books anymore. Have added the image source.

I was confused for a second because you used the phrasing 'high preload', suggesting that a higher preload causes a higher stiffness (I would suggest 'high enough preload'). Thanks for the image source, but if I interpret it correctly, there is no brake, but a simple kinematic mechanism (a link and a spring) that prevents relative rotation between the quadrants. I suppose the brake mechanism you refer to is similar to the patent you linked, which completely decouples the control surface in case of a cable breaking.

@Sanchises the image is used as an illustration.

But I still don't know what a drum brake would accomplish. Are you sure you're not referring to e.g. the trim tab drum brake like described here?

@Sanchises have updated with a more appropriate pic & description.

Let us continue this discussion in chat.

They do. See http://www.billzilla.org/aviationpage3.html, in particular:

After a few hours in the cold atmosphere cruising along, the throttle
  cables that run from the bottom of the throttle all the way out to the
  engines all shrink slightly different amounts, and so to get the same
  RPM's you often have the throttles sitting at odd angles to each
  other. This is what they looked like on descent from 37,000' one day.

What was the maintenance status of this aircraft?

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text:
What is the life limit due to metal fatigue in large bombers?
This article explains how the B-52's will be kept flying for 100 years.
Replacing the engines, electronics, etc. is one thing, but when would metal fatigue become a problem? These planes are huge and, I expect, rather heavy (at least when loaded up) and although they fly fewer cycles than passenger airliners, a hundred years is a long time.
Obviously I expect the military to be aware of this, but I'd love to hear what you folks think.

The US Air Force clearly believes that their fleet of B-52 airframes have sufficient life  to last until around 2050. They'd be in a position to know. What do you expect us to say?

Wikipedia had a whole section on all the things they replaced on the b-52 because of fatigue. My educated guess is that they just got really good at replacing parts and expect to keep it up until 2050.

"Metal fatigue" is very vague.It is going to be too broad to answer. Life can be time based, cycles, landings, air frame hours, "on condition", starts, apu hrs, and all sorts of other things. When that part is a replaceable assembly, it resets to the life associated with the fitted component. It would seem that there are enough parts and it is economical to keep changing stuff for a long time yet.

@Catch I was hoping someone would be able to say something about expected structural strength vs. age of eg. the basic fuselage. Apologies if this question is inappropriate or too vague.

The last retiring B52's will be like the axe I inherited from my grandfater, it had been in the family for centuries I was told. The head had been replaced thrice, and the handle enumerable times...

The Plane of Theseus can fly forever.

Yeah I know of Theseus. :-/ But it does not seem likely they would replace the entire fuselage -- that would entail un&installing everything else; might as well build a brand new plane at that point.

@Jpe61 - 'enumerable' means 'able to be counted' and 'innumerable' means 'more than can be counted'.

Oops, thanks

Metal fatigue and fatigue corrosion are and have been a problem since the type's introduction. They always fatigue and corrode, they always undergo expensive repairs due to corrosion. DIEGME degradation of fuel tanks has been a particular culprit, and it has been reduced with new coatings.
Bombers aren't pressurized, so the whole fuselage doesn't fatigue the way it does for airliners. The hard limit for wing spars fatigue can run into the centuries, considering that these planes don't fly all that much.
100 years is a bit of an exaggeration. The oldest B-52 in service come from the late 50s to 1962, when the production ended. So at retirement time the planes will be just 90 years old. There is a lot of B-52s sitting idle in storage, since they used to be considered strategic and fell under SALT cuts, and they're available both as spare part sources and as restorable airframes.
Why shouldn't a 100 year old plane fly? The USS Constitution is 220 years old and she's still sailing the seas, a considerably more hostile environment. It took a lot of restoration, but not quite to the extent of the Theseus' ship. Not everything is built with planned obsolescence like cars or iphones; ships and planes are built to last, as long as the owner spends the money needed to keep them up.
Keeping the old planes intact may not be cheap, but new bombers are far more expensive. The B-1B is half a billion a piece, so is the Tu-160. At the same time, most of the work the USAF does is milk runs in a threat-free environment. It doesn't call for advanced supersonic or stealth machines, it calls for something that's easy to service and cheap to run. The B-52 fits the bill better than any other bomber the USAF has. The only extant competitor is the Tu-95.
The B-52 can in theory be replaced by something even cheaper to run. Plenty of Boeing manufacturing capacity will sit idle for a long time, and, given a supply of olive drab, they'd fit the job even better. But this can't happen, because every military procurement program since the WW2 begins and ends with feature creep, doubly so in the Air Force. Only existing inventory can be kept as simple as it is.

All of this essentially leaves no choice but to keep up the current planes. Aluminum is cheap, it's silicon that's expensive, and B-52s have very little of that.

Bombers aren't pressurized, so the whole fuselage doesn't fatigue the way it does for airliners. The hard limit for wing spars fatigue can run into the centuries Thank you -- this was the kind of information I was looking for!

Back in the day the BUF (correct acronym for "D" model) airframe usage  was calculated using variable aspects of actual flight that were outside the assumptions that the engineers used to predict "ordinary" useful hours of the airframe.  If for example the plane had a 20,000 hour useful life before major overhaul or permanent grounding, that figure could be less depending on actual flight usage.  The 20k figure was on the assumption of 'ordinary' use.
Aircraft uses that were considered as "extraordinary" included flying at low level, air-refueling, carrying external (wing) munitions or shapes, flying in moderate or severe turbulence, hard landings and max gross weight takeoffs. Such uses or events or occurrences were recorded as "E hours" in the flight record book of the plane.
E hours consumed useful life hours of the plane at a higher rate. So, the total life of the airframe once operational would never match the predicted usage because of the "E" hours factor. (The effect of corrosion on airframe has been mentioned in an earlier post).

I understand why low-level ops impart stress on the airframe, but could you elaborate on air-to-air refueling also contributing to airframe stress?

Lifetime limit depends on the design and on usage.
Many aircraft have a lifetime limit given in cycles (i.e. number of takeoffs and subsequent pressurization cycles). For the B-52, flight hours are used instead (because the fuselage isn't pressurized).
Modern aircraft are designed to a specific limit, and modern CAD software allows you to predict this pretty well so the aircraft becomes no heavier than it needs to be. The B-52 didn't benefit from this, so it was overbuilt.
The move from high-altitude to low-level operations shortened fatigue life. Various modifications were carried out to strengthen the wing, for instance:

Intensive structural testing, conducted by Boeing and the Air Force in 1960, again confirmed that hard usage shortened the structural life of the B-52 aircraft. The B-52Gs and B-52Hs differed significantly from predecessor models, but design changes incorporated in the new bombers made them even more susceptible to fatigue damage. Briefly stated, the changes had been made to extend the aircraft's range, which essentially meant that while the B-52G and B-52H bombers were lighter than preceding B-52s, their fuel loads had been increased. Moreover, the overall decrease in structural weight had been achieved primarily by using an aluminum alloy in the aircraft's wings. While testing did not question the intrinsic strength of the wing, it pinpointed areas of fatigue. No one could forecast accurately when the wing failures would happen, but low-level flying and the structural strains that occurred during air refueling were expected to speed up fatigue considerably. It was estimated that under fairly similar circumstances, the operating stress placed on the new wing was approximately 60 percent higher than the stress inflicted on the wing of preceding B-52s. The anticipated problem appeared serious enough for SAC to impose stringent flying restrictions on the new aircraft, pending approval of necessary modifications. In May 1961, the Air Staff endorsed a $219 million modification program for all B-52G and B-52H wing structures. The wing structural improvement program, carried out as ECP 1050, replaced the wing box beam with a modified wing box that used thicker aluminum. It also installed stronger steel taper lock fasteners in lieu of the existing titanium fasteners; it added brackets and clamps to the wing skins, added wing panel stiffeners, and made at least a dozen other changes. Finally, a new protective coating was applied to the interior structure of the wing integral fuel tanks. The program provided for Boeing to retrofit the modified wings during the airplanes' regular IRAN schedule, except for the last 18 B-52Hs, which would get their modified wings on the Wichita production lines. Started in February 1962, the program was completed by September 1964, as scheduled.

According to GlobalSecurity:

Current engineering analysis show the B-52's life span to extend beyond the year 2040. The limiting factor of the B-52's service life is the economic limit of the aircraft's upper wing surface, calculated to be approximately 32,500 to 37,500 flight hours. Based on the projected economic service life and forecast mishap rates, the Air Force will be unable to maintain the requirement of 62 aircraft by 2044, after 84 years in service.
The B-52H was designed as high altitude aircraft, but was adapted to low level tactical maneuvers in 1960's. A number of structural improvements were made during the 1960s and 1970s to equip it to fly the more demanding low- level mission and to address other structural issues.
The airframe life for the current fleet is estimated to be between 32,500 and 37,500 hours, depending on the usage history of the individual aircraft. The estimate is based upon scaling measurements from a full-scale test structure using assumed mission profiles along with historical and projected usage information. The upper wing surface is expected to be the life- limiting structural member. As of 1999 the average airframe had 14,700 flight hours. Boeing believes with high confidence that the average number of flight hours left is 17,800, at a minimum. The "oldest" B-52H is at about 21,000 hours and only experiences about 380 flight hours per year.

Boeing makes an estimate of airframe life using fatigue testing on a test airframe, and/or modern CAD.

With some combination of regular Non Destructive Test inspections, patches and reinforcements, and in some critical areas replacement of primary structural fittings, panels and skins, and you can run an airplane forever if you can keep it safe from oxidation corrosion.
It only comes down to inspection frequency, and when and what structural parts to replace, as to whether it's worthwhile doing or not. On a commercial airliner, you get to a point where it's no longer feasible financially to either install all the patches, or inspect the airplane with the required frequency, and still make money with it.  On something like the B-52, the business case environment is a complete alternate universe (in terms of financial payback and risk analysis) where it becomes worthwhile strategically in view of the alternatives.

https://en.m.wikipedia.org/wiki/Ship_of_Theseus

I like this answer. Does the B52 have an airframe fatigue data analysis program as well? I used to analyse this data on other military aircraft and these monitoring systems meant that we could fly these airframes 50 percent longer because we were monitoring the strain gauges in real time.

@acpilot I chuckled at that one.  You can be sure a B-52 in 2040 will have recent wing planks and just about every other component that sees concentrated loads will have been changed.  Interesting that components on airliners can have a life limit, which effectively applies to the root structural part like a housing, where you can rebuild the thing totally but if it's still in the original housing, once it passes its life limit, the like-new part becomes trash.


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How is Altitude/QNH defined state when passing transition altitude?
Let's say an airplane is climbing towards transition altitude (TA = 5000 ft), and it has it's altimeter set to QNH = 1030 hPa. The altimeter is a function of pressure and QNH: altitude = altimeter(pressure, QNH). Let's say P is a pressure at TA = 5000 ft when QNH = 1030 hPa (roughly 857.74 hPa) - so P is the pressure when the airplane reaches the transition altitude.
When it reaches TA, the altimeter setting is changed to 1013.25 hPa so the indicated altitude changes as well. With the same P and different QNH, the altimeter now shows roughly 4545.8 ft. Well, this is way below transition level and transition altitude, so the altimeter should be set back to QNH = 1030 hPa. But now it shows 5000 ft again, so let's set it to 1013.25 hPa. The altitude and QNH oscillates, because the input to the altimeter (QNH) is based on it's output (altitude).
The same thing happens on a horizontal edges of airspaces (changing from REG QNH to METAR QNH) and when descending towards transition level.
I assume that pilots change the altimeter setting to "just something". But how should a software calculating the indicated pressure altitude deal with this? The point of the software is to calculate events where QNH should be changed by a pilot. The software runs after the flight and has access to resources such as airspaces, transition altitudes, METARs, GPS and pressure during the flight, and so on.

Ah, good ol' computers, they do exactly what you tell 'em to do, not what you want 'em to do...

Does this help answer your question? https://aviation.stackexchange.com/a/44088/17732

From a software perspective, I'm not sure an automatic switch over makes sense. The software calculates the "pressure altitude" from its sensor input and then applies the baro correction as provided by the pilot.

@selectstriker2 thanks, but that doesn't solve my issue. As I said before, the same thing happens on a horizontal edge of an airspace, where QNH should be different. The point of the software is to compute the the pilot's altimeter correction

Basically I'm writing a software that simulates a real pilot - it has the same information available as the pilot, and the point is to know what the pilot should do based on the information he has.

"the altimeter now shows roughly 4545.8 ft". FALSE. The altimeter now shows roughly Flight Level 45, which cannot be compared directly to altitudes. Remember, when passing TA, you change the UNIT of measurement, not just the reference pressure.

Okay, but at FL45 the reference pressure should be changed back to 1030 hPa (and the unit to ft). What if the aircraft would just peek over the TA and go right back? Or what if the same situation occurs when climbing into an airspace with different QNH?

You could define a vertical movement state in your software, let it be either climbing, descending or level flight. If the state is climbing, once you change to QNE, you don't change back, even if you are briefly below transition level.

The problem is that it is not always clear whether the vertical movement is climbing, descending or level flight. The altitude fluctuates a lot when the aircraft is controlled by hand. The best solution so far would be to filter the altitude data (using Savitzky-Golay filter, for example) and take a derivative of the filtered data to get the vertical movement state. That would not be the perfect solution, but maybe there is no way to make it more precise... Maybe I am trying to make it better than it could be

Pilots are not lazy.  They are smart enough to change it once during the climb, and not allow themselves to be drawn into silly quandaries like this.  And don’t fly right at the transition altitude.

When climbing through the TA,  usually the pilot has an intention (e.g because of ATC instruction or clearance) to be above that TA, i.e. to climb to a certain flight level. For you computer pilot, the combination of the intention and the vertical position of the aircraft should drive the altimeter setting.

My goal was to find out what a pilot would do in that situation. The solution suggested by expeditedescent seems to be the thing I was looking for - just set it when it needs to be set, and assume that nobody is going to fly at the transition altitude or at a horizontal edge of an airspace.

From a computer standpoint, I would set QNE as you pass through the TA.  If that means you are now at a "lower" flight level than the current altitude so be it.  As you descend through the TL, set  QNH.  If that altitude is higher than the current flight level so be it.  That is what pilots are going to do.  ATC directs pilots to do this with their phraseology.  "Climb FL50".  or "Descend altitude 5,000 QNH 1030".

In Canada at least, you are supposed to make the change between QNH (alt setting) and QNE (standard pressure) while in QNE airspace, whether climbing or descending; that is, right after passing the transition altitude while climbing, or just before passing transition altitude while descending.  The variable overlap zone you describe resulting from the change in barometric pressure is not critical since you are almost always just passing through on a climb or descent clearance to an altitude a couple thousand feet or more above or below. ATC sees your altitude in 100 ft increments as broadcast by your transponder, computed baro alt (transponder's pressure alt signal corrected for local baro pressure) when below the transition, then pressure alt when above, but they don't know or care what you are seeing on your altimeter while climbing through the transition as long as you level off where you are supposed to be.
So I would expect to see the altimeter setting change shortly after passing transition altitude when climbing, say within the next 500 to 1000 ft, but the pilot doesn't have to work out exactly what QNH altitude to observe to be able to make the switch right at transition alt.  Shortly following is good enough and if you are in a climb to, say, FL100, if you forget to set to 1013.25 until the TA is 8000 ft, it's not that big a deal (nobody's going to know - except for the Flight Data Recorder, and your pilot monitor nanny software that is... lol). All that matters is that you level off at your cleared FL. ATC only sees your FL, or FL corrected internally to baro, on radar so the controller isn't interested in where you switch exactly while in a climb as long as you level at the correct FL, although you are supposed to do it in a timely way.
On a descent, with a TA of FL50, I would expect to see the change from QNE to QNH while still above the TFL, say between FL50 and 60.  Even there, if you forgot to set to QNH until below FL50, if you are descending to a lower altitude, it's not critical as long as you level off at the cleared QNH altitude, monitoring software notwithstanding.
Note that Europe may have variations on this protocol, since in North America the transition level is FL180 everywhere except the high arctic (called the Standard Pressure Region in Canada), where the FLs start at the surface except where near airports.
This is the Canadian regulation on moving between Standard Pressure and Altimeter Setting zones:

Transition – CAR 602.37 – Altimeter Setting and Operating Procedures in Transition between Regions, specifies that except as otherwise authorized by ATC, aircraft progressing from one region to another shall make the change in the altimeter setting while within the standard pressure region prior to entering, or after leaving, the altimeter setting region. If the transition is to be made into the altimeter setting region while in level cruising flight, the pilot should obtain the current altimeter setting from the nearest station along the route of flight as far as practical before reaching the point at which the transition is to be made. When climbing from the altimeter setting region into the standard pressure region, pilots shall set their altimeters to standard pressure (29.92 inches of mercury or 1013.2 mbs) immediately after entering the standard pressure region. When descending into the altimeter setting region, pilots shall set their altimeters to the appropriate station altimeter setting immediately prior to descending into the altimeter setting region. Normally, the pilot will receive the appropriate altimeter setting as part of the ATC clearance prior to descent. If it is not incorporated in the clearance, it should be requested by the pilot.

"and ATC only sees your pressure altitude in 100 ft increments the entire time anyway." Additionally, the transponder always broadcasts the level as a flight level (reference 1013), regardless of the actual altimeter setting. It is then corrected on ATC end for flights below TA/TRL. So ATC will always see the correct level, no matter which QNH the pilot has selected. That's also how we can occasionally warn you of a possible wrong altimeter setting if you are flying a few hundred feet above or below cleared level.

Thanks. This is not exactly a solution, but it helped.

@expeditedescent is the QNH alt applicable relative to PA for a given altimeter setting co-displayed continuously with the FL on the screen or is it a selectable option, or do you just do a little mental calculation?

@OndrejTelka "The point of the software is to calculate events where QNH should be changed by a pilot." is your question, and my answer is basically "(should be changed) shortly after while climbing,and shortly before while descending". What other information do you need?

I wasn't sure about the overlap zone, and you said that it isn't critical. So I guess I would set it once and keep it until the plane stops climbing and starts descending, or until there is no other region with different pressure setting, as suggested by @expeditedescent. Thanks again.

Bottom line is the software should expect the switch between QNE and QNH to occur while in QNE airspace, shortly after (while climbing) or before (while descending) through the transition, say within 15 sec.  If you are looking for a hard value or tolerance, there isn't one really. It's kind of left to common sense.  The 'grey zone" in question is usually just a short phase and is not important.  If you were going to level at a FL that was just above the transition, or a QNH altitude just below it, you would make allowance for that and make the switch a little sooner than you otherwise might.

@JohnK The radar receives the current flight level (ref 1013) from the transponder. The radar processor knows the local QNH and automatically converts the flight level to altitude for flights below transition level. We only see one value, which is prefixed with an "A" if it's an altitude (not flight level). We can't see what the altimeter in the cockpit reads.

@expeditedescent I revised the last line of that para about only seeing press alt in response to your comment. Thanks.

This is related to why there is always a buffer of at least 1000ft between the Transition Altitude and the Transition Level.
If you are at 4000ft and want to climb to FL070, then once you cross the TA at 5000ft, you set QNE and climb until your altimeter reads 7000. It does not matter whether the altimeter briefly changes to 4500 (or 5500) at the instant you cross the TA since that is below what you’re climbing to.
Ditto for setting QNH when descending through the TL.

Seems the good answer, in addition TA/TL are not managed the same way in the US/Canada and in the rest of the world. In the rest of the world the altimeter is not set based on your actual altitude, but as soon as you are cleared to a level or to an altitude, so there is no "oscillation" problem around the TA. See this for when to change: "this is done irrespective of how far above or below the TL/TA you are at the time", but in relation with the intent, as DeltaLima commented below the question.

@mins What do pilots elsewhere do if ATC stops their climb or hands them off before they pass TA? The US/CA way, we still have the correct QNH set.

In non PAN-OPS method, ATC assigns a new altitude or level, the crew should uses the datum associated with the new clearance for altitude reportings. This means if ATC pauses a climb/descent using some altitude/level value, the datum can change, but if the pilot initiates the leveling, the datum is kept until ATC assigns a new vertical target. See scenario 3 here for forgetting to reset to QNE when initialy cleared to descend below TL but leveled by ATC before TL. Ultimately, the SOP can impose a specific procedure.


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How are both squawk and altitude transmited when operating a Transponder in Mode C?
I know that in Mode $3$ (which includes Mode A and Mode C) the aircraft transmits $12$ information pulses. That corresponds to $2^{12}=4096$ squawk combinations in Mode A which are sent to ATC to identify the aircraft. In Mode C, all $4096$ combinations are used to send the pressure altitude of an aircraft to the ATC.
Since there are $12$ usable information pulses, when operating in Mode C, there is no way to transmit the squawk code, which in my mind raises an obvious question: What if I suddenly squawk $7700$ due to an in-flight emergency? Or $7600$, radio failure? If I continue to operate in Mode C, it seems that there is no way that ATC would know that I am in any kind of trouble. How is this issue resolved and is my understanding correct?

Mode 3/A and Mode C are not the same thing.

Squawk codes (Mode A replies) are transmitted in response to Mode 3/A interrogations. Altitude codes (Mode C replies) are transmitted in response to Mode C interrogations.
Both Mode A and C replies use the same 12 pulse encoding, but the radar that asked the question knows how to interpret the answer (assuming there is no FRUIT or garbling, but that is another topic).
If the transponder is in altitude reporting mode (i.e. it replies to Mode C interrogations), it will also reply to Mode 3/A interrogations.
Thus, if you squawk 7700 and you transponder is switched on (either Mode A only or Mode A/C), then code 7700 will be the response to the next Mode A interrogation from a radar. If your transponder responds to Mode C interrogations as well (i.e. altitude reporting is on), the radar will receive altitude information in response to Mode C interrogations.


text:
Do most airport use one and only one runway for landing?
Do most airports (especially busy ones) use only one runway at a time for landing? For example, I know Heathrow uses only one of its runways at a time (although they might switch to another half way through the day).

Half way through what?

Does this answer your question? What determines in which direction a runway is used?

Many "busy" international airports (LAX, CDG, AMS,...) have more than 2 parallels runways. Even if using form landing only and another one for take off only, it would still allow the use of another runway. You should restrict your question to international airports with exactly 2 runways.

Statistically speaking, most airports only have one runway

I just remember some international airport use parallel landings. SFO is a famous example.

In general, any runway can be used for both takeoffs and landings. However, switching back and forth requires substantial safety margins. If you can use one runway for just takeoffs and another for just landings, efficiency goes up. If those runways are parallel, efficiency goes up again. This is why major airline hubs tend to have pairs of parallel runways.
Averaged over a day, the number of takeoffs and landings should be about the same, so the normal mode would be to split the runways as evenly as you can. If the number of runways isn't even, the last runway will often alternate throughout the day to mitigate short surges in one or the other.
As to which runways are used for what, the ones used for landing should be as far from each other as possible to maximize lateral separation of arriving traffic on instrument approaches. (Departing traffic mostly separates itself.) So, if you had four runways organized as two pairs, you'd expect the "inner" one of each pair to be used for takeoffs and the "outer" one of each pair for landings.
In the case of Heathrow specifically, runway usage is largely dictated by noise abatement agreements with nearby towns, rather than what makes the most sense operationally.

Depends on the airport and the traffic.  For instance, at Reno (RNO) airlines and other large planes generally use 16R/34L, smaller planes use the parallel (and shorter) 16L/34R.  However, it's not at all unusual for smaller planes to use 7/25 if there's no conflicting traffic.  (Especially since crosswinds can sometimes be pretty strong on 16/34.)

I don't agree that "substantial safety margins" are required for runways with mixed departure and arrivals. Departing and arriving flights use roughly the same amount of time on the runway - typically around 45-60 seconds. You can do landing-takeoff-landing-takoff with 1 minutes between each flight just as well as you could do several takeoffs or landings each with one minute between

@J. Hougaard: Though you need appropriate spacing/separation for wake turbulence.

@jamesqf There a mix of arrivals and departures is actually an advantage, since you will automatically have twice the spacing between consecutive departures and consecutive arrivals

Airports will usually divide their active runways about evenly between takeoffs and landings. KATL (Atlanta Hartsfield Jackson) has 5 runways, and currently operates 2 for takeoff and 2 for landing. Most airports that can operate more than 2 runways simultaneously will use them all, unless the traffic is just very low.
Heathrow is exceptional in that it is one of the busiest airports in the world, and only has 2 runways.

Do you know where I can find information on how runways are assigned at each airport? For example, Beijing has 3 runways. I want to know whether two of them can be used simultaneously for landing.

How far apart are they? That is key - they need to be far enough that wing vortex from one landing aircraft doesn't impact the adjacent runway. I looked that up for the USA, if I recall 4300 feet was needed.

Heathrow has 2 strips and 4 runways as each strip has a runway in each direction.

@GdD It's completely normal to refer to a strip as one runway although it can be used from either end. I don't think anyone is in doubt about what zymhan means by two runways. Claiming Heathrow has four runways would be misleading in most situations.

@Teodorism you can follow live ATC or flightradar24 during few hours to see actual assignation.


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What is the Difference between mogas and avgas?
Could anybody tell me the primary differences between mogas and avgas?

lead and alcohol

Related: Why is AVGAS so much more expensive than car gas?

The main difference is avgas is based on completely different chemistry, paraffin (the flammable component of candle wax) and mogas is based on aeromatic hydrocarbons (like benzine).  (Forget about alcohol - mogas MUST be alcohol free)
The paraffin base makes avgas much more stable (so it can be stored a long time) and it has a much lower Reid Vapor Pressure (a much higher boiling point, to avoid boiling, or vapor lock, at altitude.)
Avgas's paraffin chemistry makes it more dependent on tetraethyl lead to achieve its octane rating, which is much higher than mogas in the first place, whereas mogas's naturally more detonation resistant chemistry, lesser vapour pressure requirements and lower octane requirements allowed for lead to be eliminated in the 70s using other means to achieve its octane rating.
The main practical differences in general aviation are mainly that it's not a good idea to store an aircraft with mogas in the tanks for long periods because it will go bad sooner (not more than 3-6 months with modern mogas) and you will get vapour lock more readily with mogas so you can't fly as high, and heat exposure to the fuel system has to be controlled (such as by using air-blast shrouds on fuel pumps).  Vapour lock is less of a problem on gravity fed systems because there is positive pressure all the way through the system.  Pump-uphill fuel systems have suction in the fuel lines which is like climbing to a higher altitude.
Pilots generally only use mogas in carbureted engines meant for 80-87 avgas but you can use 94 octane mogas in a 100 octane non-turbocharged engine without problems (in Canada, commercial bush operators can use mogas by STC/STA in supercharged engines like R-985s, so the octane rating isn't that big a deal on engines with 8:1 compression).
I use mogas in my own airplane, who's low compression 80-87 engine is much happier on it than 100LL (not having to clean lead fouled plugs regularly).  The most noticeable differences is it makes a lot more black soot in the exhaust for some reason, with the same leaning practices.  I add the occasional tank of avgas periodically because the lead has a beneficial lubricant effect on valve seats.
Another minor issue is leaded aviation fuel doesn't like synthetic oil.  Synthetic oil's chemistry can't keep the lead is suspension so it forms "lead paint" inside the engine.  This was a problem when Mobil AV1 aviation oil was introduced (there was a big class action lawsuit).  On mogas, synthetic oil is not a problem (I use Aeroshell 15W50 semi-synthetic in my plane).

An excellent FAQ on gasolines here http://www.runyard.org/jr/CFR/autos_gasoline-faq_part1.html      With 'paraffins', John K is using the old nomenclature (paraffins/olefins). Today, for single-bonded hydrocarbon chains, the term 'alkanes' is more usual...

The engine in my certificated airplane, Lycoming O-360-A1F6D, needs 100LL
FAA Type Certificate...........286
Rated horsepower...............180
Rated speed, RPM.............2700
Bore, inches.......................5.125
Stroke, inches....................4.375
Displacement, cubic inches........361.0
Compression ratio ..... 8.5:1
O-360-A:  100/100LL      This can't change without an STC for the engine, and a 2nd STC for the plane.

Yes the STC requirement is a given in a certificated airplane, although owners of homebuilts can use whatever they want.  On a strictly technical level, your 100LL O-360 engine would run perfectly fine on 94 oct mogas.  I was a member of a glider club that had thousands of hours on O-360s running on premium unleaded in a brutal glider towing application.  I was quite surprised when the Cdn STA was introduced that it included supercharged engines. A bush operator I once worked for started running his Beaver on it in the early 90s and all he noticed was the rear plug fouling problem went away.

At the end of your first paragraph, I think you meant to say the avgas must be alcohol free.  Mogas almost always contains alcohol these days.

@Gerry When I say Mogas I'm referring to automotive fuel sold for aircraft use.  That has to be alcohol free.  You can get alcohol free fuel from suppliers if it's for a non-road use so an airport selling Mogas will be sure it's alcohol free fuel.  Unless the Mogas comes from a trusted and confirmed source, you have to test it yourself to make sure there is no alcohol in it (simple water volume test).  I used to get gas from service stations (premium unleaded in Canada generally doesn't have alcohol added, only regular) but still I would test it to make sure.

Chemically speaking, The difference in the fuels is the inclusion of lead-based additives that increase the Octane rating of the fuel, which are otherwise banned for use in other settings due to the negative effect on air quality. The other common use of leaded fuels I can think of is in auto racing, which also doesn't particularly prioritise air quality. Unleaded high-octane fuels do exist for aircraft engines, but those engines have to be certified to use those fuels, a long and expensive process. This is why they are less common.
Octane rating itself measures how resistant the fuel is to detonation.
Engines run at a specific level of compression. Simplistically, More compression produces more power, which is important in smaller piston engines. But having too high a compression ratio causes the mixture in the cylinder to detonate on it's own before the proper point in the timing cycle where it should be ignited by the spark plug. This is called 'knocking'.
In the best case, the result is increased fuel consumption as the ECU (ironically) throws more fuel into the mixture to reduce the possibility of detonation (at least in fuel-injected car engines this the case). In the worst case, the result is damage to the engine as uncontrolled detonation can put large unwanted loads on the crankshaft and the con-rods. Power output will be reduced in any case, which can be a massive issue for heavily laden aircraft attempting to climb in high or hot conditions.

"Avgas has a lower and more uniform vapor pressure than automotive gasoline so it remains in the liquid state despite the reduced atmospheric pressure at high altitude, thus preventing vapor lock" https://en.wikipedia.org/wiki/Avgas

Mogas and avgas are very similar ; the difference is in ratio of high octane to lower octane components . The major group of high octane components are aromatics; the xlyenes with octanes well over 100. Also some parafinics like octane ( which is 100 octane ). Also some products from alkylation ( "alky") but I don't know the specific compound names. Xlyenes are expensive because they are produced in expensive complex reformers which use high temperature high pressure hydrogen and often platinum catalyst.  Also the competing use for xylenes as the raw material for polyester. Alkylation is less expensive using concentrated sulfuric or hydrofluoric acid at below ambient temperatures. Most components in mo gas come directly from distillation ( pipe still) and cat cracking ( very high temperature but easy to contain low pressure,) so are relatively inexpensive. I doubt there is much alcohol in avgas as it has 10 % less energy per pound.

100LL is essentially 94 octane premium ‘mogas’ mixed with tetra ethyl lead to boost its octane rating.

"Avgas has a lower and more uniform vapor pressure than automotive gasoline so it remains in the liquid state despite the reduced atmospheric pressure at high altitude, thus preventing vapor lock" https://en.wikipedia.org/wiki/Avgas

But again, essentially the only change here is the addition of tetra ethyl lead to 94 octane gasoline.


text:
How is the A320neo engine different from the A320ceo engine?
I've looked up at internet about the differences. And the only difference they mention is that the new engine has a higher bypass ratio (making it more fuel efficient), quieter and has an improved range. Are there any other differences other than these?
Are the engines lighter than its predecessor (are they made of lighter alloys?)
Do the new engines have the reduction gearbox which lacks in the ceo engines?
And what is TAPS II combustor technology?

Which engines are you talking about? Both the A320ceo and the A320neo come with two engine choices.

CFM LEAP -1A engines

The predecessor of that engine would be the CFM56 engine, which is (among others) used on the A320ceo. You should edit the question to ask about these engines rather than the aircraft. Note that the CFM56 was also used on the 737 NG and the LEAP is now used on the MAX.

@Johnson you should put the engine model in the question so that it is clearer at first read without digging into comments

Other good parameters to compare are linked to temperature, pressure and other parameters (EGT, N1, N2, EPR, fuel flow) at a specific flight phase (take off or cruise)

It is a very large question and it will be difficult (even with all information) to give a strict answer.
Both LEAP-1A (A320neo family) and CFM56-5B (A320ceo family) are turbofan engines which means they have two cores (HP and LP core) and two flows, and where total airflow is created by a Fan. As you said, LEAP-1A has a larger diameter allowing higher by-pass ratio (efficiency improvement) and lower rotational Fan speed (noise reduction). Besides, OPR (Overall Pressure Ratio) is greater (~40:1 vs. ~33:1) and lead to a performance improvement too.
Nevertheless, even if LEAP-1A has a slightly greater max thrust (~155kN vs. ~140kN), we cannot affirm there is "a range improvement" since they do not operates on same aircraft. If it's true here, it is more appropriate to compare aircraft range than engine range. Moreover, thrust is calculated for an aircraft flight mission (by Airbus, Boeing, etc.) and then generally given to engine manufacturers as input for conception.

Now, to answer more specifically your questions, LEAP-1A service entry was in 2016, more than 20 years after CFM56-5B first flight. Therefore LEAP engines gather a lot of improvements resulting from years of research and maturity tests. So yes, there is others differences between these engines (you can find public characteristics on manufacturers or specialised websites - even wikipedia get a lot of information actually).
1. Are the engines lighter than its predecessor (are they made of lighter alloys?)
Material is probably one of the field where you can find best improvements in aeronautics the last decades, for both aircraft and engines. In particular, many advances have been made with composite materials.
When comparing CFM56-5B and LEAP-1A, the most significant (and literally the most viewable) point is about Fan material. For a CFM56-5, fans are probably made of steel or nickel alloy (I don't know exactly but these are common for old generation engines). In a LEAP engine, composites are used for fans with titanium at leading edge. This allow, amongst others, a lower number of blade (18 blades) and larger chord: fan mass reduction despite larger diameter, aerodynamic efficiency, etc.
But is LEAP-1A really lighter than its predecessor CFM56 ? Not sure, remember that the diameter is larger. A quick search on google give 2900kg for LEAP-1A and 2400kg for CFM56-5B, but I don't know if it was calculating in the same way.
Note that other improvements are made in high temperature parts (like HP turbine) both in cooling and material resistance resulting in a higher combustion temperature (again there is an efficiency improvement).
2. Do the new engines have the reduction gearbox which lacks in the ceo engines?
No, both LEAP-1A and CFM56 do not include gearbox. CFM international has never developed an engine with it. This is a manufacturer choice as the gearbox lead to an extra mass and often extra maintenance costs. In the other hands, gearbox give advantages by decoupling LP turbine / booster and fan speed and remove one constraint to optimise each component.
As @Bianfable said in comments, it is a little bit awkward to talk about ceo and neo engines as Airbus manufacture these aircrafts with 2 different engines. For example, Pratt & Whitney PW1000G turbofan on A320neo include a reduction gearbox..
3. And what is TAPS II combustor technology?
TAPS (Twin Anular Premixing Swirler) is a combustor technology developed by GE aviation. While CFM56-5B used SAC (Single Annular Combustor) or DAC (Double Annular Combustor),  TAPS is a newer type of combustor used for GEnX engine (Boeing 747-8 and 787). The version II is the scaling version for LEAP engine. The main idea is to limit rich combustion zone (mainly responsible for NOx).
Take a look to this FAA report for interesting details.


text:
Why Heading Indicator is not magnetic itself and need magnetic compass?
I read this while I was preparing for my knowledge test:

The heading indicator is not direction-seeking. It is important to
  check its indication frequently and reset it with reference to the
  magnetic compass.

and I am doing this all the time during flight time.
Why don't small aircraft manufacturer make the Heading Indicator magnetic instead of gyro?

What would you do when flying in an area of magnetic unreliability?

Compass readings during turns are inaccurate and sometimes display turns when you are heading straight but accelerating. As such you need something that is referenced to the airframe turning itself. This is where the gyro comes in handy. Since it's referenced to the airframe and relatively unaffected over short periods of time it gives you your heading when your compass can not. You can also "time your turns" using the turn coordinator and a stop watch should your heading indicator fail. It should be noted that a timed turn will only work if the turn remains coordinated (no slip or skid) further more most turn coordinators are set up for 2 minute turns.
The errors are as follows

If on a northerly heading and a turn is made toward east or west, the initial indication of the compass lags or indicates a turn in the
  opposite direction. The lag diminishes as the turn progresses toward
  the east or west where there is no turning error.
If on a southerly heading and a turn is made toward east or west, the initial indication of the compass needle will indicate a greater
  amount of turn than is actually made. This lead also diminishes as the
  turn progresses toward east or west where there is no turn error.
If a turn is made to a northerly heading from any direction, the compass indication when approaching northerly heading leads or is
  ahead of the turn. Therefore, the roll out of the turn is made before
  the desired heading is reached. If a turn is made to a southerly
  heading from any direction, the compass indication when approaching
  southerly headings lags behind the turn. Therefore, the roll out is
  made after the desired heading is passed. The amount of lead or lag is
  maximum on north / south headings and depends upon the angle of bank
  used and the latitude of the aircraft.
When on an east or west heading, no error is apparent while entering a turn to north or south. However, an increase in airspeed
  will cause the compass to indicate a turn toward north. A decrease in
  airspeed will cause the compass to indicate a turn toward south.

The constant need to reset it is related to gyroscopic precession.

COST! What you need is a remote magnetic indicator. Some more advanced small planes have them. It's becoming less of the problem nowadays because even small airplanes get modern glass cockpits.

That is called a flux gate.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Does "resume own navigation" also mean "altitude your discretion"?
In VFR flights from class C, I sometimes get resume own navigation, altitude your discretion after departure and sometimes just resume own navigation.
Does resume own navigation alone mean altitude your direction as well?
Update:
Let's assume scenario below for KSNA and to be more specific:
Pilot to Clearance Delivery: 529J with request
Clearance Delivery: 529J go ahead
Pilot to Clearance Delivery: 529J is Cessna 172/u west side parking, requesting
El Toro departure to Chino with information Bravo
Clearance Delivery to Pilot: After Departure turn left heading 080, Maintain VFR at or below 2400, SoCal on 124.1, SQUAWK 0210
Pilot: reads back …
Pilot starts taxi then take off with proper radio communication with ground and tower. After departure Tower hands pilot over to SoCal.
Pilot to SoCal (initial call): SoCal 529J departed John Wayne, 1100 climbing, requesting 3000 to Chino
SoCal to pilot:  529J resume own navigation
Here is the confusion, sometime SoCal comes back with only resume own navigation. Does this mean pilot can climb to 3000 or altitude restriction for 2400 still valid?

When you receive only the resume own navigation instruction, is that ever following an altitude instruction that would need to be cancelled? Altitude is always your discretion in VFR flight in class C unless otherwise instructed.

KSNA departure has altitude/heading restriction on departure. After departure Tower  hands you over to SoCal Approach. SoCal issues the 'resume own navigation' sometimes follows by 'altitude your discretion' and sometime doesn't.

resome own navigation means any navigation instructions are no longer in effect and you may fly as you wish.
If an altitude restriction has been given, you must maintain that restriction until you hear "altitude your discretion."
If no altitude restriction had been given then you may of course change your altitude.

I added a scenario to my question.

At this time, the definition of "resume own navigation" is very varied from group to group. ATC Controllers say that if there is an altitude restriction, they have to clear it. So safest thing to do is to ask for clarification if you had an altitude restriction/not told "altitude your discretion" that would continue into the "resume own navigation" exactly what you are doing now.
Source

That's what I always do but I wanted to know if I am doing the right thing

@PMoubed Then you are doing the right thing then, under the current system.

@PMoubed Also, you should put that into your question that you do do this.


text:
Can I use my aviation handheld transceiver on MURS?
Is there a regulation or rule about using handheld aviation transceivers e.g. Icom A-24 for ground to ground communication on MURS frequencies?
Can I just use Icom A-24 for ground to ground? or do I need FCC licence?
Update:
Can I use my handheld aviation transceivers (Icom A-24) for ground to ground communication? or do I need a FCC license?

MURS: Multi-Use Radio Service. Specific to the US. Five frequencies from 151.820 to 154.600 MHz. Many modulation modes allowed, some channels can use narrow band (2.5 kHz), some can use wide band (5 kHz).

You asked for legal opinion, so the main "legal" reason would be that a radio must be type-accepted for the service for which you want to use it. So unless Icom A-24 is MURS type accepted, and it is not, then it's illegal to use it.
You don't need a special FCC license. FCC says this about licensing:

MURS is licensed by rule. This means an individual license is not
  required for an entity to operate a MURS transmitter if it is not a
  representative of a foreign government and if it uses the transmitter
  only in accordance with Section 95.1309. There is no age restriction
  regarding who may operate an MURS transmitter.

But the transmitter itself must be marked as MURS transmitter. FCC has this to say about that:

A MURS transmitter must be certified by the FCC. A certified MURS
  transmitter has an identifying label placed on it by the manufacturer.

There is technical reason as well which makes it impossible to use it on higher VHF frequencies: Above 137 MHz, the traditional modulation type is FM. Aviation VHF is AM. So even if you wanted to talk to MURS users, you wouldn't be able to do so normally due to different modulation types used. Another technical issue is frequency coverage. A-24 can transmit 118.000 MHz to 136.975 MHz. I don't know if it's possible to unlock it for extra coverage (but I'd be surprised is that was possible, due to use case), but with default frequency coverage you can't go high enough to reach MURS frequencies.
UPDATE:  I just checked and it seems that AM is actually allowed on MURS. So it is, and you can somehow unlock the A-24 to operate on those frequencies, you could technically speak to other AM MURS users, but again it wouldn't be legal due to licensing system used for MURS.


text:
How serious is an impact like the 10/2017 Delta Airlines suspected bird strike?
Recently, there was an incident where a Delta Airlines charter flight carrying the Oklahoma City Thunder basketball team was struck by an "unidentified object". Delta's official statement claims that

Delta flight 8935, operating from Minneapolis to Chicago-Midway as a charter flight for the Oklahoma City Thunder, likely encountered a bird while on descent into Chicago. The aircraft, a Boeing 757-200, landed safely without incident; customers have since deplaned and maintenance teams are evaluating.

While I do not agree with the UFO label that this story seems to have run with, I am shocked that a bird (especially at such an altitude) could cause such severe damage to the nose cone (even at such speeds).
Is this characteristic of a bird strike and how severe would this incident have been had the collision been with the windshield?

This is PPRuNe's take on it https://www.pprune.org/rumours-news/601207-delta-airlines-hits-ufo-ok-here-we-go.html

"I do not agree with the UFO label that this story seems to have run with" Why not? The plane was clearly hit by an object. That object was at 30,000ft, so it seems reasonable to describe it as flying. And they don't know what the object is, so it is unidentified. "UFO" means what it says. It does not mean "alien spacecraft".

Hi @DavidRicherby, (for better or worse) it's a simple, undeniable, fact that (in English and many languages) "ufo" has come to mean "alien spacecraft".  I am the #1 hater of words changing meaning (I spend half my life trying to explain to people how to actually use "apocryphal") - but you are, simply, in the only possible meaning of word meanings, "wrong" to asset that "ufo" does not mean "alien spacecraft".

@Fattie Fair point. I should have written "[UFO] doesn't only mean 'alien spacecraft'."

To repeat myself, I'm totally with you though  :)

To put it another way, if we knew it was an alien space craft, it wouldn't be unidentified.

other things aside, why do you assume that a bird like turkey vulture cannot be an alien spacecraft? :)

@quetzalcoatl Because Turkey is an alien country?

I admit my question was somewhat poorly worded. I understand the technical distinction (and do agree) but I think the term has become synonymous with "extraterrestrial spacecraft".

Bird strike happens all the time - almost on a daily basis. See avherald : there are 9 instances of bird strike in the past 7 days at the time this answer is written. Usually it is ingested into the engine (which usually turns out to be a non-issue), other times it impacts the cone or leading edge of the wings or knocks off a pitot tube.
While a few incidents make it to mainstream news from time to time, bird strikes are a common occurrence in the aviation industry. It is an unusual situation, but not a dangerous situation if the pilots handle it properly.
How severe if it collided with the windshield? The windshield is tested against this type of impact during certification. At worst the outer layers will crack, and the pilot will execute the landing using the "cracked windshield" procedure (Yes there is a procedure written for this scenario).
A note about the UFO: technically it is an UFO, an Unidentified Flying Object. It could be a bird, a drone, weather balloon etc. Examination of the impact area might reveal what the object was.

+1 I didn't know how to handle the UFO part in my answer =)

Is the term "UFO" still used as its origin meaning in technical documents?

UFO != Alien aircraft. Unless it is an uindentified flying object owned by someone from outside the USA, then it is indeed an alien aircraft. But not of the extraterrestrial sort. But just because we don't manufacture aircraft outside the ionosphere yet.

@Mindwin so if I went to the moon and folded a paper airplane there I would have a extraterrestrial aircraft.

@ratchetfreak indeed. But not of the xenobiological kind of extraterrestrial UFO.

If you observe the photos of the incident, you will find that the dent was in the radar dome in the nose, which is not nearly as strong as the windshield. Doesn't need to be, it isn't part of the pressurized section. Note also that the dome was not punctured, so whatever hit it was fairly blunt, like a large bird. The absence of blood on the dome is a bit curious, though... maybe the photo just doesn't show it.
Note also that the radar dome didn't fracture apart, it just buckled but remained intact and remained in position. It did what it was designed to do - take an unexpected hit and not shatter or dislodge and possibly FOD the engines.
Modern airliners have been tested extensively for bird strikes, especially on the windshield, as a breakage or intrusion at speed there could be catastrophic to the aircraft, as in rendering the pilots blind or unconscious.
This isn't a very serious incident. The radar dome was buckled, but that's about all that happened. Radar domes on airliners have suffered similar damage in flight from large hailstones, without seriously impacting the aircraft's ability to fly.
As it is, the flight crew responded exactly as they should have, and the flight landed without further problems. Had the bird hit the angled and much stronger windshield, and not the blunt, forward facing radar dome, it would most likely have just glanced off, maybe leaving a nasty blood smear.

Some of the pictures I saw seemed to indicate the aircraft was wet. Some rain before landing could explain the lack of blood or other physical signs. (One of the avherald commenters pointed this out.)

Animal impacts don't have to be bloody.  I remember one time when a rabbit decided to jump out in front of my car as I was doing 60+ MPH down the Interstate.  I had no time to react, and I felt the impact against the car's frame.  When I reached my destination, I looked at the front of the car and saw no damage and no blood anywhere.

I once flew with a 727 pilot who told us about striking a goose that penetrated the radome and the bulkhead. The copilot had blood and guts on his legs when they landed.

There are a couple of assumptions that need to be cleared up.

While I do not agree with the UFO

But the official word was not UFOs... It was labelled a likely bird strike.

especially at such an altitude

This question address the fact that birds can fly very high and there was a confirmed bird strike upwards of 37500 ft.

could cause such severe damage to the nose cone (even at such speeds).

You're really underestimating the forces here. The bird metioned in the last question could have weighed upwards of 20 lbs. That's 20 lbs, mach 0.8, hitting a thin composite radome.

Is this characteristic of a bird strike

YES. Here is an AV Herald search result for bird strikes. They happen all the time. If you randomly click through the search results you will see either pictures or descriptions of bent radomes, broken props and struts, or engine flamouts.
The beauty of it all is these planes all landed relatively safe (even the miracle on the hudson!)

how severe would this incident have been had the collision been with the windshield?

It depends. If the pilots are both still conscious and can see they can fly the plane. In theory they could even "fly blind" like they were flying IFR (landing would be tricky depending on the runway equipment).
Heck a pilot got half sucked out of a plane due to a faulty window and even he lived
Planes are like cars. They balance functionality with sturdiness. The vehicle has done its job if you can walk away from an accident.


text:
Is the NTSB hostile to pilots, as depicted in the movie 'Sully'?
This is based upon events portrayed in the movie Sully.  If the film is taken at face value, what we basically see is a (fairly brazen) stitch-up attempt by the NTSB (National Transportation Safety Board), where they try to steer an investigation towards a predetermined conclusion of 'pilot error' (and very nearly succeed) using:

Naively unrealistic computer simulations that assume a pilot would divert towards the nearest landing strip immediately after a birdstrike without needing any time to evaluate the damage to their aircraft, attempt to diagnose and troubleshoot the problem, or coordinate with air-traffic-control.
Similarly unrealistic simulations using real pilots who have been trained/conditioned to divert immediately after the simulated birdstrike.
The deliberate omission of the fact that the pilots only succeeded in their simulation attempts after multiple failed training attempts, up until the pilot involved in the actual incident calls BS on the whole charade.

The only motivation posited in the film for the NTSB's attitude was that the insurance company would have preferred a conclusion of 'pilot error'.  Thus, my questions are:

Is the film's portrayal of the NTSB accurate, either in terms of having a general anti-pilot bias or in terms of the particular investigation depicted having had an anti-pilot bias?
Why would the NTSB care about acting in the interest of insurance companies (particularly to the extent that they'd be willing to throw pilots under the bus to do so)?
Does an insurance company avoid a payout in the case where an aircraft is lost due to pilot error (as opposed to mechanical failure, birdstrike, or other unavoidable scenario)?

Small comment/IMHO: Blaming it on pilot error is not good, since it is never a root cause. At the end of the day, somebody permitted the pilot (with certain training, schedule, knowledge etc.) to take on the responsibility that he had. The general public tends to overlook this though, and settles with 'pilot error' as the resonable cause of the accident.

I never trust Hollywood to deliver anything other than entertainment, especially when aviation is involved. Sully himself is on record saying that the film does not fairly portray the NTSB or the way they acted in this particular case. The real Sully insisted the names be changed for the film since the movie treats the NTSB investigators as the "villains" of the story, painting them to be more vindictive and out-to-get-'em than they were in real life.

If you'd rather watch than read for further insight, try this: https://www.youtube.com/watch?v=RuxCBYAaZ9M - a documentary on the incident. Of note here is that it contains comments by some of the actual investigators. Consider that it's their job to apply all due diligence to find the facts without bias. One investigator even commented on the pressure to not taint Sully as a hero; to do their job properly, they cannot allow themselves to be affected by any such outside influences .

And one other point: "Sully" is a dramatic movie. Drama needs heros (the crew) and villains. The writers chose to make the NTSB the villains of their story. It was the writers' choice, irrespective of any actual facts.

One final point: the role of any safety board is not to lay blame or find accountability, but to objectively identify root cause and any contributory cause in order to make recommendations which can prevent recurrence and improve safety. There have been incidents where the findings of a safety board contradicted those of the local police force. There are jurisdictions where any incident involving wrongful death requires a guilty party, no matter the facts. The local police choose their culprit, even if the safety board finds that the accident could not have been forseen.

Frankly, I'm impressed. Based on the title, I came here expecting 4 out of 5 'Close' votes as opinion based, yet the question is well thought out and the answers are all very good quality. Congrats on a great 2nd question!

Clint Eastwood made a movie where the government is the villain?  Who could have foreseen it?

Relevant: http://www.slate.com/articles/arts/culturebox/2016/09/sully_is_the_perfect_fantasy_for_the_post_fact_era_of_the_brexit_and_trump.html

At least they didn't blame Canada.

@user19474 But it was obviously Canada's fault! They let their geese just roam around into busy U.S. airspace. :)

If you report your child missing, you will likely feel that the police are treating you as a suspect. That's because they are. That doesn't mean they're biased and not properly investigating. They just have to run down every plausible theory, perhaps ultimately finding it unfounded. So yes, they investigated whether it was at all possible for a pilot to divert to land immediately because that's a reasonable question to ask, not because they expected that to happen. Many actual NTSB reports will say that something was possible, but that no crew could reasonably have been expected to do it.

I think it is quite unfair to paint the NTSB investigators as villains just for the dramatic effect when nothing of the sort happened in real life.

It is the job of the NTSB to investigate all possible reasons for the accident. It includes pilot error among other things. They were doing precisely that in the actual investigation. Among other things, the NTSB concluded that:

The captain’s decision to ditch on the Hudson River rather than attempting to land at an airport provided the highest probability that the accident would be survivable.

The simulations carried out by the NTSB were part of the investigation and were much more elaborate:

The pilots were fully briefed on the maneuver before they attempted to perform it in the simulator. The following three flight scenarios were flown:
(1) normal landings on runway 4 at LGA, starting from an altitude of 1,000 or 1,500 feet on approach;
(2) attempted landings at LGA or TEB after the bird strike, starting both from zero groundspeed on takeoff from runway 4 at LGA and from a preprogrammed point shortly before the bird strike and loss of engine thrust; and
(3) ditching on the Hudson River starting from 1,500 feet above the river at an airspeed of 200 kts.

Note that the NTSB clearly mentions that the pilots were briefed before the simulation. NTSB noted clearly in its report that immediate turning of the aircraft after the bird ingestion did not reflect what could've been done in real world:

The immediate turn made by the pilots during the simulations did not reflect or account for real-world considerations, such as the time delay required to recognize the bird strike and decide on a course of action.

The simulations (along with the case where there was a 35 second delay to account for pilot response) was done entirely by the NTSB with no input whatsoever from the flight crew. As The Guardian notes:

And then the investigators – not Sullenberger – asked a pilot to wait 35 seconds before attempting an airport return. That flight didn’t make it. Consequently, the NTSB was unequivocal in its declaration that the Hudson was the right call.

Actually, the movie was so inaccurate in the portrayal of the NTSB that the real people involved asked the names of the investigators in the movie to be changed:

... a draft script included the names of real-life NTSB officials, but Sullenberger - who is an adviser on the film - requested they be taken out.
He said, ‘These are people who are not prosecutors. They are doing a very important job, and if, for editorial purposes, we want to make it more of a prosecutorial process, it ain’t fair to them,”’ said Hanks.

There is no evidence to determine that the NTSB acted in the interest of insurance companies (or anyone else) in this investigation. The situations in which an insurance company is liable depends on the particular policy (as far as I know, liability is usually for negligence).
While the investigation may not be perfect, there was no kangaroo court anytime during the investigation. There was no attempt at public lynching, as The Guardian notes:

In fact, in his memoir, Sullenberger reflects that he was “buoyed by the fact that investigators determined that Jeff and I made appropriate choices at every step”

There was no cover-up by the NTSB and there was no Kangaroo court (you can easily look up the public hearings in this case) to pin everything on the flight crew on behalf of somebody else. Though not perfect, there is nothing to suggest that the investigation was not conducted professionally.
It is sad that the movie portrayed officials performing their duty as villains just because it was decided that the people would rather have the ancient good Vs evil show in the movie rather than the truth (while I'd have to agree that the movie would've looked more like documentary otherwise, that is no excuse).
The problem though, is that more people will be seeing the movie than reading the report or looking up the actual investigation that people will have a entirely uncalled for negative opinion of the NTSB, which may affect the future investigations. As Robert Benson who carried out investigation on the Flight 1549 noted in an article:

"I do not know why the writer and director chose to twist the role of the NTSB into such an inaccurate depiction. .... The movie may actually be detrimental to aviation safety. Pilots involved in accidents will now expect harsh, unfair treatment by investigators. They and others who see the movie will now believe that the NTSB enters into any investigation with preconceived notions, and that we are intent on destroying reputations. Simply untrue. The NTSB is the best friend an airline passenger never gets to meet."

When you consider that they took what's essentially a relatively short event (bird hits plane, plane forced to land) into a full on Hollywood blockbuster, you "need" a villain...and I suspect they didn't want to make Birds the enemy, so why not some big government agency? But I agree, they could have shown how professional they are at NTSB and that all govt agencies don't work against the folks they're tasked with watching out for.

@BruceWayne Indeed, it's surprising that in this day and age and with the political leaning in Hollywood they didn't make the Insurance Agency the 'evil' and give the government a pass.

@BruceWayne: make Birds the enemy -- THAT's a movie I'd want to watch!

This answer has removed my last reason for watching the movie - curiosity about how to turn that incident into a feature length film. It seemed to have all the wrong structure: resolution of the main climax minutes after the first deviation from normal, a lot of cooperation, no villains.

@BruceWayne - Another option might have been to cast the media as the main villain.  Especially given that as the other answer points out, it was CBS who put forward an article headlined "Sully Could Have Made it Back to LaGuardia".

@slebetman uhmmm...almost certainly one of the most famous films of all time

@Jamiec, came here to say that, only mildly disappointed that you beat me to it! :)

@BruceWayne What I found disappointing (I've only seen the movie preview) was how tense/emotional the pilot and ATC's voices sound, compared to how their voices sound on the real recording of their conversation.

@Jamiec: Those birds didn't attack a passenger jetliner. I was thinking more along the lines of snakes on a plane... but birds

@Jamiec and also responsible for the fact that every time I hear a flock of birds now there's always a slight increase in my fight/flight response. Alfred Hitchcock!

I'm surprised the real pilot even signed the movie off...

I've been wondering if an immediate turn to airport wouldn't make it on real hardware due to loss of hydraulic pressure, etc. because the APU isn't on.

No, they are not.  The NTSB simply investigates accidents to determine the root causes of the accident and to make recommendations as to how to improve aviation safety.  It has no bias nor does it play favorites.
The NTSB investigation of US Airways flight 1549 was the most unrealistic element of the Sully movie.  Director Clint Eastwood portrays The NTSB as trying to do a hatchet piece on Captain  Sullenberger at the behest of both US Airways and the insurance underwriters for the A320 airplane which was lost. In reality the real NTSB report for Cactus 1549 reads nothing like that.  Even the principle NTSB characters in Sully are fiction, the NTSB sunshine hearing is totally different and the simulator run-throughs happened months before the hearing ever took place.  See below.
As I understand it, Eastwood needed an antagonist for the film tho make it more relatable to the audience.  The NTSB seemed the only and logical choice for the role.
Most NTSB investigators scoff at the investigation portrayed in Sully; my favorite take was from an investigator who said that 'Sully' was about as close to a real NTSB investigation as 'Sharknado' was to real meteorology.
The basis for Eastwood's take on the NTSB investigation in Sully seems to be a CBS news story published over a year after the accident which talked about run throughs of the accident using A320 simulators which showed flight crews could have turned back to LGA or TEB if they immediately reacted to the bird strike and turned back.  What Eastwood seems to missed in that story was that both the NTSB and Airbus concluded that the simulator scenario was not a reasonable facsimile of the actual events and stressors which the crew of Cactus 1549 faced that afternoon on Jan 15, 2009 and both parties stated that ditching in the Hudson was the only reasonable alternative in this situation.
If anything the recommendations from the NTSB's report on Cactus 1549 praised Capt Sullenberger and FO Stiles for how they handled the incident, praised US Airways for keeping life vests and rafts onboard its domestic flights despite no federal regulatory requirements to do so, scrutinized Airbus for having complicated engine out checklists which were not easy to follow by a crew at low level and scrutinized the FAA for not having regulations in place for the use of child safety seats for infants and young children on revenue flights.
The NTSB rarely reacts or makes scathing rebukes in its reports; one example of the NTSB characterizing a player in a negative light was the NTSB report of the Gulfstream G650 prototype crash in Roswell, NM, in 2011.  Here the NTSB faulted Gulfstream - and rightfully so - for a recklessly run flight test program and its obstinance and refusal to cooperate with the investigation after the accident.

"'Sully' was about as close to a real NTSB investigation as 'Sharknado' was to real meteorology" - Thanks, that's a great quote.  Pretty much says it all.

@aroth wait, Sharknado wasn't real?

@aroth Careful, hollywood might now make a Sharknado movie and everyone may think it's real or possible.

A large cylindrical object with wings has landed in the Hudson after strange geese were seen flying near Mars...

Was that edit really worth bumping this question to the front page?

The NTSB does so routinely find pilots at fault for virtually everything under the sun (with all other factors and actors only as "contributing") that when they don't, as in US1549, it's now a notable event.
However, I don't think it's fair to call that hostility. Regulators and vendors have (at enormous cost) engineered virtually all safety problems out of the system except for human error, so it's not surprising that human error remains by far the most significant problem--despite decades of trying (mostly in vain) to figure out how to better train us.
The downside of vesting pilots with final authority over their flights (especially in an emergency) is that necessarily comes with final responsibility for those same flights.  That means the pilot is nearly always at fault in an accident, at least as far as the regulations are concerned. If anything, that leads to cynicism or even hostility from the pilots' side when dealing with the NTSB et al.

They don't, really. Not when professional pilots are involved. Sure, the majority of incidents are blamed on pilot error, but the majority of incidents are stupid mistakes by amateur pilots in light aircraft misjudging conditions and ending up in a situation way outside their training (flying into IMC, getting lost due to navigation errors, runway incursions for lack of situational awareness, running out of fuel because they forgot to check fuel levels before takeoff, etc. etc.).